Miniaturized cathode-ray tube with precisely oriented electrostatic deflection electrodes

ABSTRACT

A character display system has a plurality of small cylindrical side-by-side cathode-ray tubes about 0.8 inch in diameter and less than 4 inches long, aligned to form a line of individual characters. The tubes have structure for precisely aligning the characters uniformly including an electron gun fashioned to center the electron beam by means of electrostatic deflection electrode pairs held in two glass beads oriented with a seven pin miniature glass stem to produce two normal deflection axes. Similar electrode structure is employed for a plurality of electrodes in the gun formed of a rectangular-shaped blank held at opposite ends in the two beads, and a set of snubber springs is affixed to one such electrode oriented toward the stem to and in centering the gun within the tube cylindrical walls.

United States Patent [72] Inventor Horst H. Blumenberg Owensboro, Ky.

[21] Appl. No. 861,788

[22] Filed Sept. 29, 1969 [13] Division of Ser. No. 843,296, July 22, 1969 [45] Patented Sept. 14,1971

[73] Assignee Kentucky Electronics, Inc.

Owensboro, Ky.

[54] MIN IATURIZED CATHODE-RAY TUBE WITH PRECISELY ORIENTED ELECTROSTATIC DEFLECTION ELECTRODES 4 Claims, 6 Drawing Figs.

[52] US. Cl 313/78,

[5 1] Int. Cl ..l-l0lj 29/74,

H0 lj 29/82 [50] Field of Search 313/69, 69 C, 70, 70 C, 92 B, 78

[5 6] References Cited UNITED STATES PATENTS 2,411,205 l III 946 Green et a]. 313/80 Primary Examiner-Robert Segal Attorney-Laurence R. Brown ABSTRACT: A character display system has a plurality of small cylindrical side-by-side cathode-ray tubes about 0.8 inch in diameter and less than 4 inches long, aligned to form a line of individual characters. The tubes have structure for precisely aligning the characters uniformly including an electron gun fashioned to center the electron beam by means of electrostatic deflection electrode pairs held in two glass beads oriented with a seven pin miniature glass stem to produce two normal deflection axes. Similar electrode structure is employed for a plurality of electrodes in the gun formed of a rectangular-shaped blank held at opposite ends in the two beads, and a set of snubber springs is afiixed to one such electrode oriented toward the stem to and in centering the gun within the tube cylindrical walls.

PATENTED SE? 4 I971 SHEEI 1 0F 2 Q o loll DEFLECTION CHARACTERDGENERATOR AN SELECTION CIR U FIG.I

INVENTOR HORST H. awmmaene BY W 6% 34%,

ATTORNEY MINIATURIZED CATHODE-RAY TUBE WITH PRECISELY ORIENTED ELECTROSTATIC DEFLECTION ELECTRODES This application is a division of my copending U.S. Application of the same title, Ser. No. 843,296, filed July 22, 1969.

This invention relates to character display devices and more particularly it relates to cathode-ray tube displays for generating a line of separate characters in individualside-by-side tubes.

Display devices responsive to electronic signals to generate visual characters such as numbers or alphabets are known, which operate in different modes. Many such devices are deficient in several important aspects.

If mechanical devices are used, they do not follow electrical signals adequately or quickly enough and they are difficult to synchronize.

Cathode glow and phosphor display devices are low in brightness. Most of these provide parallax problems and do not show parts of the characters formed. Also they are not adaptable to variations of characters and such symbols ad the dollar sign or letters in Hebrew or Arabic which require special tooling. Also a limited number of different characters can be displayed, in general.

Cathode-ray tube devices in the prior art have not been competitive in price with low cost display tubes. Some have required custom tubes with built in masks or special features for generating character shapes. Generally, an entire line of characters is formed on a large screen cathode-ray tube which is not adaptable to the space and aspect ratios required in many instruments and data processing applications, which should require custom built envelope sizes and specialized deflection systems. Individual tubes used for generating each character would be too expensive in both tube design and system requirements when using prior art techniques. For example, oscillographic centering structure such as horizontal and vertical centering potentiometers used in orienting placement and skew of the different characters placed in a line by means of standard CRT techniques would be prohibitive in price when applied to a plurality of individual tubes.

Accordingly, it is an object of this invention to provide im proved character display devices correcting the foregoing deficiencies.

A more specific object of the invention is to provide specially constructed cathode-ray tube indicia generating devices which are economically and technically feasible within required geometry and electrical restrictions imposed in producing side-by-side characters of uniform size and skew in very small spaces with tubes less than one inch in diameter.

Therefore, in accordance with this invention, individual cathode-ray tubes places side-by-side in line to form a line of characters are each made with cylindrical envelopes of less than four inches in length and 0.8 inch in diameter to display individual characters of any desired shape by scanning an electron beam electrostatically along two normal axes.

To provide acceptable alignment each tube has an electron gun with electrodes precisely positioned and oriented to produce a beam centered on the phosphor screen raster area of approximately 0.625 inches maximum deflection provided for character formation. This alignment is accomplished in part by use of rectangular shaped electrode plates which are held in two spaced glass beads oriented carefully in the center of the cylindrical envelope relative to a seven pin miniature stem to define two normal deflection axes precisely within less than 3".

Those features of novelty afforded by this invention together with further objectives and advantages of the invention are illustrated by the preferred embodiment shown in the accompanying drawings, wherein:

FIG. I is a schematic block diagram of a character display system incorporating a plurality of side-by-side cylindrical cathode-ray tube character generating devices in accordance with the provisions of this invention.

FIG. 2 is a perspective view of a cathode-ray tube character generator afforded by the invention.

FIG. 3 is a plan view of an electrode plate structure provided by the invention.

FIG. 4 is a perspective view of a snubber electrode assembly afforded to provide precise spot centering within the cylindrical tube envelope afforded by this invention.

FIG. 5 is a partly broken away view of a character generating tube with a snubber electrode in place, and

FIG. 6 is an elevation view of the electrode assembly as afforded by the invention with connection leads shown schematically.

In FIG. I a set of separate cylindrical envelope CR display tubes 10, 10' etc. is aligned along horizontal deflection axis 12 with their phosphor faceplates substantially in the same plane. Each tube 10 has a vertical deflection axis 11 which intersects at the center of the display with the horizontal deflection axis 12.

When forming a line of separated characters, the alignment and skew is critical if misalignments visually detectable are to be avoided. For this reason a character forming tube for presenting a single character is critical in construction and must afford a combination of features which will provide precise centering and deflection alignment in each individual tube without the necessity for external adjustment or manipulation of electronic circuits. Conventional tube construction techniques in a tube of the very small size required with a screen diameter of less than one inch which would permit the beam to be off center as illustrated in tubes 10 and 10 by the dots, or which would allow deflection skew as illustrated in tubes 10" and 10" would be unacceptable in forming a line of characters. The eye is very sensitive in sensing character alignment and even a small degree of skew or misalignment is readily notices as evidenced by viewing typewritten text when a type bar is slightly displaced, for example.

Character displays of any design can be generated for electrostatically deflecting the cathode-ray beam to form the numerical characters 2 illustrated, of other desired pattern. Deflection techniques of this type are well known and are represented by the block circuit diagram 15. The state of the art may be exemplified for example by reference to U.S. Pat. No. 3,432,845 issued Mar. I 1, 1969, where numerical characters are produced. It is to be noted that a CRT display of the type provided by this invention is not restricted to any one set of characters are produced. It is to be noted that a CRT display of the type provided by this invention is not restricted to any one set of characters or any limitations on variations or total number of characters possible. Also, by use of a P-l phosphor, the brightness significantly exceeds that generally available with cathode glow, phosphorescent or other displays which generate their own light source.

Each tube is separately driven at grid lead 17 and the horizontal and vertical deflection axes at leads I8, 19 by character generator subsections I6, 16 etc. To produce the desired line of text. In order to display a line of characters on individual tubes it is significant that the tube shape is cylindrical or equivalent nonflared shape with substantially symmetri cal sidewalls permitting the tubes to be placed closely together sideby-side along axis 12 and does not constitute a flared out screen section found in conventional cathode-ray tube oscillograph tubes.

Thus a tube 10 is preferably constructed as shown in FIG. 2, with a cylindrical envelope having an axis 32 along which an electron beam is nominally directed in absence of electrostatic deflection voltages. Electrostatic deflection plates permit the tubes to be placed side by side without interference between tubes. In this tube, the electron gun 30 is physically positioned in a precise manner to assure that the electron beam is directed along center line 32. This requires care in orienting each gun and deflection electrode exactly in place to be held firmly by a pair of glass beads 31. The beads are oriented in the region of exhaust stem 39 and the miniature seven pin button to precisely align the deflection axes with respect to the pin socket positions. This is done by straps or metallic posts welded carefully in place between the electrodes and the pins inside the tube envelope to serve as leads and mounts to orient the deflection plates and stem in exact alignment. To assure the centering of the beam within the cylindrical tube envelope, a set of special snubber springs is provided as hereinafter described to center the electron gun at a position remote from the stem.

In order to facilitate alignmemt and jigging for the precise electrode spacing and to seal the electrodes in the glass bead without distortion, electron lens electrodes 41, 53, 54, 55 are made rectangular in shape as shown in FIG. 3, to thus be embedded in the beads at opposed ends. To permit electron gun flexibility with this preferred structure, the centered beam aperture is selectively punched to the desired size for each electrode but, otherwise, the various electrodes are similar, to provide both low cost and better electron gun electrode alignment as well as performance.

FIG. 4 shows one such electrode 41 with a larger aperture 44 used to mount snubber prings 42 by welding at spots 43, near the opposite ends extending into the beads. Thus, as mounted within the tube illustrated in FIG. 5, the bead 46 holds electrode 41 so that the snubber springs 42 engage the interior glass sidewalls of the cylindrical tube at four positions to assure centering of the electron gun structure with the screen and tube axis. The snubber springs may be directed toward the tube stern and plug pins to produce improved centering by relating the gun axis of the tube structure at the stem mount position and a critical position near the deflection elec-' trodes.

This critical snubber mount position is referenced in place in FIG. 6, where the snubber electrode or shield is held at ground potential be connections to lead 65. The snubber plate 41 is physically mounted between beads 50, 51 in a position intermediate the two pairs of deflecting electrodes. The accelerating potential is applied between terminals 65 and 68.

The internal connections to the seven pins are illustrated, where grounded pin 65 leads to electrodes 41, 54, 55 and one electrode 63, etc. of each pair of deflection electrodes. Other connections are made to the heater pin 66 and to the grid pin 67. Each deflection axis is available at a separate pin 69 and 7] connecting with respective deflection plates 64 and 62. A focus electrode such as cylinder 61 or an equivalent apertured plate structure is connected at pin 70 to make available all the necessary electrode controls in a miniature seven pin stem.

The gun structure has to be inexpensive to produce a com petitive display tube and yet very critical tolerances must be met. These tubes are constructed with a centering requirement for an undeflected beam to lie within /2 millimeter of the center of the tube in the scanning region on the phosphor coated screen. Also the horizontal and vertical deflection axes are oriented to within three degrees of a reference axis defined by the orientation of the pins in the seven pin miniature stem.

These requirements must be considered in view of the sensitivity of the beam to electrode positions and defects, and the normal tolerances of jigs with thermal changes of dimensions and stresses, etc. The very small dimensions of the tube with a nominal cylinder diameter of 0.788 inches, tube length of 3.5 inches overall and useful screen deflection of 0.625 inches, make the requirements even more critical.

These requirements are met, however, by the array shown in FIG. 6 where the electrodes are all aligned precisely between glass beads 50 and 51, held rigidly in place by the rectangular structure of the various electron gun electrodes 53, 54, 55 and 41 spaced along the gun structure. This physically orients the electrodes precisely enough to direct the beam along a well defined axis which is centered within the cylindrical tube envelope by the snubber springs to direct an undeflected spot precisely along the axis of the tube.

Also the deflection plates are oriented along normal axes by the beads 50 and 51 to provide closely aligned deflection axes. Simple electrode structures, such as the deflection plate 64 which is a singleflat plate bent along a straight line, provide for a minimum of distortion of the beam by defects, corona or the like.

The rectangular lens structure with the oppositely extending tabs mounted in the pair of parallel glass beads permits also an improved and simplified cathode mounting. Among their advantages is the simplicity ofjigs for holding the electrodes exactly in position while affixing a glass bead.

A cylindrical metallic cathode cup 56-59 is affixed by a tab to the rectangular plate 52 without an intermediary ceramic disc or other insulator. The cathode cup 59 is preferably surrounded by a cylinder shield 60 which is affixed to the plate by a suitable tab portion. The shield 60 serves simultaneously to electrically shield the cathode emission surface, provide proper heat conduction and dissipation characteristics and permit precise axial spacing of the cathode relative to control grid 67 while maintaining exact alignment of the cathode with the axis of the tube.

What is claimed is:

l. A character display system having a plurality of side-byside cathode-ray tubes, each displaying separate characters comprising in combination,

each said tube having an unflared envelope whose internal dimension perpendicular to the longitudinal axis does not exceed 0.8 inch, and an overall length less than four inches, said tube having substantially symmetrical sidewalls with a closed transparent end member including a phosphorescent coating upon which the cathode ray impinges and two pairs of electrostatic deflection plates to deflect the cathode-ray beam in two dimensions to produce a pattern upon said phosphorescent coating representative of characters such as alphanumeric displays, and further having a glass stem with a set of terminal pins extending therethrough at a predetermined orientation to said deflection plates,

means fonning separate characters upon the coating of separate tubes by deflecting a single cathode-ray beam striking said coating over pattern identifying a legible symbol in each tube, with the plurality of tubes aligned in said side-by-side array to provide an intelligible line of messages text thereupon by producing different deflection potentials at said electrostatic deflection means for each tube of said plurality,

a set of electrodes comprising an electron gun in each said tube for forming and directing a discrete beam to said coating all being held in precise position by portions thereof being held by a pair of spaced glass beads extending along the length of the set of electrodes, each deflection electrode of one pair of said two pairs comprising a single flat plate bent at an intermediate position and held by an integral tab extending into said beads, and tab means for attaching the deflection electrodes of the second of said two pairs to said beads for aligning said two pairs for scanning two normal axes within a tolerance of less than three degrees relative to said predetermined orientation,

whereby each of said tubes forms a character in said line precisely oriented and positioned to prevent visibly detectable misorientation of characters caused by mispositioning or skew.

2. A character display system as defined in claim I wherein said stem with said set of plug pins comprises a standard miniature seven pin socket assembly and has respective electrodes and connections made within the tube from the separate electrodes to separate pins as follows:

one electrode of each of a pair of deflection electrodes connected to respective pins,

at least one accelerating electrode connected to a pin,

a control electrode connected to a pin,

one of two heater leads connected to a pin,

a focus electrode connected to a pin, and

the other electrodes of each deflection pair, a cathode and the other heater lead connected commonly to a seventh least one set of the deflection plate pairs positioned to produce a deflection magnitude in the order of 0.625 inches upon said coating. 

1. A character display system having a plurality of side-by-side cathode-ray tubes, each displaying separate characters comprising in combination, each said tube having an unflared envelope whose internal dimension perpendicular to the longitudinal axis does not exceed 0.8 inch, and an overall length less than four inches, said tube having substantially symmetrical sidewalls with a closed transparent end member including a phosphorescent coating upon which the cathode ray impinges and two pairs of electrostatic deflection plates to deflect the cathode-ray beam in two dimensions to produce a pattern upon said phosphorescent coating representative of characters such as alphanumeric displays, and further having a glass stem with a set of terminal pins extending therethrough at a predetermined orientation to said deflection plates, means forming separate characters upon the coating of separate tubes by deflecting a single cathode-ray beam striking said coating over pattern identifying a lEgible symbol in each tube, with the plurality of tubes aligned in said side-by-side array to provide an intelligible line of messages text thereupon by producing different deflection potentials at said electrostatic deflection means for each tube of said plurality, a set of electrodes comprising an electron gun in each said tube for forming and directing a discrete beam to said coating all being held in precise position by portions thereof being held by a pair of spaced glass beads extending along the length of the set of electrodes, each deflection electrode of one pair of said two pairs comprising a single flat plate bent at an intermediate position and held by an integral tab extending into said beads, and tab means for attaching the deflection electrodes of the second of said two pairs to said beads for aligning said two pairs for scanning two normal axes within a tolerance of less than three degrees relative to said predetermined orientation, whereby each of said tubes forms a character in said line precisely oriented and positioned to prevent visibly detectable misorientation of characters caused by mispositioning or skew.
 2. A character display system as defined in claim 1 wherein said stem with said set of plug pins comprises a standard miniature seven pin socket assembly and has respective electrodes and connections made within the tube from the separate electrodes to separate pins as follows: one electrode of each of a pair of deflection electrodes connected to respective pins, at least one accelerating electrode connected to a pin, a control electrode connected to a pin, one of two heater leads connected to a pin, a focus electrode connected to a pin, and the other electrodes of each deflection pair, a cathode and the other heater lead connected commonly to a seventh pin.
 3. A character display system defined in claim 1 wherein the center of an undeflected beam appears within a one millimeter diameter circle on the coating at the center of said cylinder.
 4. A character display system as defined in claim 1 with at least one set of the deflection plate pairs positioned to produce a deflection magnitude in the order of 0.625 inches upon said coating. 